CN1100282C

CN1100282C - Digital optical switch

Info

Publication number: CN1100282C
Application number: CN97195341A
Authority: CN
Inventors: 诺贝特·凯尔; 姚汇海; 克里斯平·扎瓦兹基
Original assignee: Heinrich Hertz Research Institute Information Technology Berlin Co Ltd
Current assignee: Heinrich Hertz Research Institute Information Technology Berlin Co Ltd; Fraunhofer Institut fuer Nachrichtentechnik Heinrich Hertz Institute HHI
Priority date: 1996-06-05
Filing date: 1997-05-30
Publication date: 2003-01-29
Anticipated expiration: 2017-05-30
Also published as: DE19623888A1; EP0902910A1; KR20000016372A; WO1997046909A1; JP2000514569A; CN1221496A; EP0902910B1; CA2257533A1; US6233377B1; DE59706102D1

Abstract

A digital optical switch with two input terminals and two output terminals should satisfy the extensive uses of optical switches. The conditions for adiabatic mode development can be flexibly adjusted depending on the planned use for said switch, the technological production thereof still being simple. In the digital optical switch according to the invention, the first incoming wave guide (WG1), with regard to the second incoming wave guide (WG2) in the input section (S1), and the third outgoing wave guide (WG1'), with regard to the fourth outgoing wave guide (WG2') in the output section (S2), are symmetrical with each other in cross-section, index of refraction and arrangement in relation to the direction in which the light spreads. Structured electrodes have a tapering effect on the wave guides and are adjacent thereto, and an electrode driven arranged in the output section is electrically driven.

Description

Digital optical switch

Technical field

The present invention relates to a kind of digital optical switch.

Background technology

For the broadband optics signal transfer in the Optical Transmission Network OTN, for being used for walking around the changer of failure system or optical cable and for the space switching in the transmission optics net node, optical switch is attractive parts.The switching of LAN (LAN (Local Area Network)) camera cable of optical signalling is that it is further used in telecommunication, microsystems technology and auto industry in the broadband optics reverberator of computing machine and sensor and the automobile.The different switch parameters of these different application requirements, as little crosstalk, little switch power consumption, polarization independence and wavelength sensitivity.

Prior art is derived from US PS 4 775 207 or the applied physics communication on October 19th, 1,987 51 (16), 1230-1232 page or leaf and EP 0 457 406.Invention grows up on this basis.

What the publication of delivering for the first time related to is at LiNbO ₃Be arranged as the digital optical switch of X-shaped shape on the matrix, the width of two close waveguides is different in the input field.Output waveguide is lighted by electrodes surrounding from contact.Have between two waveguides of drawing from contact point between two input waveguides of input field and in the output area angle θ (θ＜＜Δ β/γ), Δ β is the mean difference of the propagation constant of two symmetric patterns, γ is the lateral wave constant in the waveguide environment.For this four terminal numbers word electrooptical switching, under the situation of considering asymmetric input waveguide on its width, handoff procedure is based upon on the basis of adiabatic model differentiation.Thus, by output waveguide is carried out control corresponding, realize on purpose in the waveguide of DOS (digital optical switch), only introducing a kind of definite pattern.

Introduced digital optical switch in EP 0,457 406, the input waveguide of input field has unsymmetric form in this switch, and the output waveguide of output area has asymmetric or symmetric form, and available power is switched.In input field and the output area asymmetry of waveguide form by linear ground and crooked shape ground approaching mutually or away from the waveguide realization.Compare with above-mentioned DOS, by means of the mutually approaching curve form of input area or output area mutually away from waveguide should be able to realize that parts shorten.

For 2 * 2DOS, in the prior art of described layout, realized in the input and/or the formation of output area that at least in part adiabatic model develops required asymmetric of principle.Adiabatic light is propagated and can only be carried out under waveguide parameter has the situation of very little change, and like this, the luminous energy that incides on the switch with a given basic model (basic mode) also keeps with this pattern basically, and any patterns of change does not take place.If the luminous energy that is in the low mode level incides on the switch very much, so, light will be by having the output waveguide transmission of high index, so when the transmission of the luminous energy in the switch is carried out with adiabatic method basically, will the higher extinction ratio of generation.

In addition, well-known, digital optical switch is made up of 1 * 2-Y-shunt.In ECOC ' 95-Brussels conference, reported about digital thermal optics 1 * 2 switch on the polymer matrix (referring to Proc.21stEur.Conf.On Opt.Comm., the 1063-1065 page or leaf), in this piece report, waveguide is buried, between the output branch road-0.12 ° angle is arranged, the thermode of two branch roads is covered fully.When giving an output branch road heating, light will be in the branch road of not heating, then, when power controlling when 130mW is between 230mW, the extinction coefficient of measuring in the heating branch road is better than 20dB.When power controlling during about 180mW, extinction coefficient reaches 27dB.

For the first time introduced 1 * 8DOS in another piece report of ECOC ' 95-Brussels conference, it is made up of (referring to Proc.21 the cascade of three 1 * 2 switches ^StEur.Conf.OnOpt.Comm., 1059-1062 page or leaf).Also used heat-luminous effect in this solution in polymer waveguides, it can produce big variations in refractive index under very little control voltage, and can on purpose produce mode performance thus.

Summary of the invention

Task of the present invention is, introduces the digital optical switch that two input ends and two output terminals are arranged, in this switch, but the condition that develops according to range of application flexible adiabatic model, but technically can simple realization.

The task of invention is finished like this: digital optical switch of the present invention comprises input field and output area, and develops the part of controlling the influence of light spread state according to adiabatic model; Have first input waveguide and second input waveguide in the input field, these two waveguides are approaching mutually gradually, certain in its interaction area a bit, and in this some contact; Have the 3rd output waveguide and the 4th output waveguide in the output area, from above-mentioned that to overseas certain of interaction area a bit these two output waveguides gradually mutually away from; The waveguide of output area links to each other with the waveguide of input field,

In digital optical switch, the direction of propagation with regard to light, input field first input waveguide that begins to mention is identical mutually on xsect, refractive index with the 4th waveguide with second input waveguide and output area the 3rd output waveguide, and they are symmetrical on the layout about optical propagation direction, have the structure electrode of localized variation width and waveguide and be adjacent to arrange, the electrode of input field and the electrode of output area design can be by automatically controlled.

By separately the waveguide of two same form in the input and output district arrange and make they near and working electrode to the wedge effect of waveguide, solution of the present invention can be carried out parameter regulation respectively in each waveguide arm, develop to realize adiabatic model.Can realize asymmetrical waveguide thus, and needn't in the forming process in DOS district, carry out preconditioning, because be provided with input field and output area in the method for the invention as the translation field with the waveguide geometry shape.DOS of the present invention, that be based upon on the adiabatic model differentiation basis has shown stair-stepping break-make performance, and this makes on-state of determining can keep long time, as the connection voltage or the electric current that have added on threshold value.Because its electrode working range is modulability flexibly, DOS of the present invention has bigger allowable error, has reduced and has connected voltage or the accurate necessity of regulating of Current Control.In addition, such DOS also has wavelength sensitevity.

In form of implementation of the present invention, stipulate

-the first input waveguide and second input waveguide in the input field with the θ angle (θ＜＜Δ β/γ) near each other gradually point-blank, Δ β is the mean difference of the propagation constant of two symmetric patterns, γ is the lateral wave constant in the waveguide environment.The 3rd output waveguide and the 4th output waveguide in the output area with identical θ angle point-blank gradually mutually away from.Or

-the first input waveguide and second input waveguide, curve ground is approaching mutually in the input field; The 3rd output waveguide and the 4th output waveguide also be curve ground mutually gradually away from.In the special formation of the embodiment that mentions, the input waveguide of input field is identical with the output waveguide of output area on xsect and refractive index, and the output waveguide of their layout and output area is symmetrical.Or

-the first input waveguide and second input waveguide in the input field with at the θ angle (θ＜＜Δ β/γ) approaching mutually point-blank.The 3rd output waveguide and the 4th output waveguide, in the output area curve ground mutually away from.Or

-the first input waveguide and second input waveguide, curve ground is approaching mutually in the input field.The 3rd output waveguide and the 4th output waveguide at the θ angle (θ＜＜Δ β/γ) point-blank mutually away from.

Stipulate that in other form of implementation the electrode wedge shape landform that contiguous waveguide is arranged covers waveguide or has wedge structure, and is arranged in same one deck of waveguide.

In this form of implementation, for waveguide, that the method for invention can be used is known in other embodiments, from III-V family semiconductor, LiNbO ₃, glass, Si-Ge mixed crystal, SiO ₂With the material of selecting in the condensate,,, on purpose regulate the light velocity of propagation difference in two waveguides of input field promptly according to the heat-light or the electricity-luminous effect of waveguide material with the function that can in all variations, realize wishing.Production for the digital optical switch of inventing can have very wide material range of choice in this way, also will further enlarge possible range of application.

What other form of implementation of invention related to is the control variation of electrode.Regulation, with the electrode of input waveguide disposed adjacent in the input field and with the output area in the electrode of output waveguide (it and input waveguide minute surface symmetry or point symmetry) disposed adjacent design can be by automatically controlled.

These forms of implementation with invention have illustrated the very big changeability that realizes the DOS of invention.Asymmetric adjusting of carrying out by means of electrode control during symmetrical structure, the light between input field and output area waveguide that these forms of implementation relate to symmetrical structure, the output area output waveguide of input field input waveguide is propagated and the change of refractive index and the change that light is propagated in the waveguide adjacent with controlled electrode under its effect.

The electrode pair waveguide has the zone of wedge effect to guarantee adiabatic waveguide in input field and output area.By means of the condition that the controlled electrode in the input field is regulated adiabatic model, make that the light velocity of propagation in two waveguides of input field on purpose produces difference DELTA β.First input waveguide and second input waveguide in the input field with the θ angle (θ＜＜Δ β/γ) point-blank mutually near and contact, the 3rd output waveguide and the 4th output waveguide in the output area with same θ angle from contact point begin point-blank mutually away from.The θ angle is corresponding with adiabatic model differentiation condition, and it is in this wise little, make that corresponding input waveguide occurs or the pattern or the asymmetrical pattern of symmetry according to whether heating in the central area, the central area is that input field waveguide straight line enters joint and output area output waveguide and leaves a little region here.Therefore can the symmetric pattern of central area be transferred to the output waveguide of hope by the heating power of the accurate adjusting electrode adjacent with output waveguide.When heating power was enough big, symmetric pattern was propagated in the waveguide of not heating all the time, and asymmetric mode is propagated in the waveguide of heating.Therefore, the method for invention is embodied as single mode with each waveguide portion of input field or output area.When at least one stage casing, district of the DOS that invents, promptly in input field or the output area, when waveguide is formed shaped form, can regulate the condition that adiabatic model develops with simulating.

According to prior art, in the array that a plurality of known DOS form by cascade, owing to the different size of input waveguide branch road needs tapered region, it amplifies the structure length of array in undesirable mode, does not allow the insertion decay of optimizing.In the form of implementation of the present invention (input waveguide of input field becomes minute surface and point symmetry with the output waveguide of output area, but and has realized the DOS of two-way operation) these defectives do not appear, because field distribution only needs the xsect all the same with all waveguides to conform to.Therefore, the DOS of invention can be used as array component in an advantageous manner.In addition, compare with 1 * 2-Y switch of mentioning in the prior art, this array component has very compact layout.And 1 * 2-Y switch just can have in the array of being made up of four this switches and the DOS identical functions of inventing.

This an array is based upon on the polymeric matrix in another form of implementation of the digital optical switch of inventing.Two linearities near or away from θ angle≤0.1 that comprises of waveguide °.Wedge shape ground covers waveguide to electrode on the buffer intermediate layer by being arranged in.In this preferred embodiment, by the control to electrode, the refraction index changing amount of respective waveguide can be adjusted to and is Δ n＞0.0015.Because the good may command mode of production, the use of polymer waveguide makes many architecture advances approach.In addition, polymkeric substance also has very big heat-spectrum number, i.e. the change of temperature produces very big refraction index changing and very little electric conductivity.Can many opticses be integrated in the substrate with hybrid technology by means of polymer technology.

Further introduce inventive embodiment by means of accompanying drawing below.

The accompanying drawing summary

Fig. 1 has schematically shown the sandwich construction planimetric map of DOS of the present invention on the polymeric substrates;

What Fig. 2 showed is the xsect of sandwich construction AA ' section among Fig. 1;

Fig. 3 shows is BPM (light Law of Communication) simulation of straight-through (" bar ") state of the DOS that introduces among Fig. 1;

Fig. 4 shows is BPM (light Law of Communication) simulation of staggered (" cross ") state of the DOS that introduces among Fig. 1;

Fig. 5 shows is to the measurement curve of the relation of the automatically controlled power of Fig. 1 DOS electrode under output area waveguide luminous power and the pass-through state;

Fig. 6 shows is to the measurement curve of the relation of the automatically controlled power of Fig. 1 DOS electrode under output area waveguide luminous power and the staggered state;

What Fig. 7 showed is the measurement curve of describing break-make performance controllability.

Embodiment

The waveguide that DOS sandwich construction on the polymeric substrates has comprised the symmetry with identical cross-section and refractive index among input field S1 and the output area S2 is schematically described among Fig. 1.Be furnished with two waveguide WG1 and WG2 in the S1 of input field, they have

corresponding input end

1 and 2, angle θ between the two=0.08 °.Two waveguide WG1 ' and WG2 ' that separate with equal angular θ are arranged in the S2 of output area, and it has corresponding output terminal 1 ' and 2 '.Waveguide among waveguide among the input field S 1 and the output area S2 is a symmetric arrangement.On one 3 inches silicon wafers, produce waveguide by means of the standard polymers guide technology with PMMA (organic glass).Waveguide has the xsect of 7 μ m * 7 μ m.Two waveguides of input field or output area are at a distance of 250 μ m, and whole DOS length is 25mm.Four waveguide WG1, WG2, WG1 ' and WG2 ' are by four wedge electrode E1 that are superimposed upon on the corresponding waveguide, E2, and E1 ' and E2 ' cover.In the DOS of invention, the propagation performance of light develops by adiabatic model and characterizes.For each waveguide WG1, WG2, WG1 ' and WG2 ' can be by control corresponding electrode E1, and E2, E1 ' and E2 ' realize the condition that adiabatic model develops.The method of invention allows to generate the DOS that two input and output are arranged for the first time on polymeric substrates.

Fig. 2 has described the xsect of 2 * 2-DOS on the polymeric substrates in the mode of planimetric map.Be furnished with SiOx cushion BB as on the silicon base S of heat radiator.The thick cushion TB of 3 μ m that is made up of ptfe plastic is used to reduce loss and protects ducting layer W not make moist, and is provided with waveguide WG1 in ducting layer, WG2, WG1 ' and WG2 '.At each waveguide WG1, WG2, WG1 ' and WG2 ' go up to arrange corresponding thermode E1, and E2, E1 ' and E2 ' be as last one deck, make that the waveguide below it is topped by wedge shape ground.

The function of the DOS that develops based on adiabatic model of the present invention can be well by means of Fig. 3 and Fig. 4 explanation.In the first of Fig. 3 and Fig. 4, introduce respectively and illustrated arrange with the X-shaped shape, the heated waveguide WG1 of electrode, WG2, the input field S1 of WG1 ' and WG2 ' and output area S2.Shown each waveguide WG1 in the part subsequently, WG2, among WG1 ' and the WG2 ' under straight-through (" bar ") state or staggered (" cross ") state, the possible approach of light wave propagation.

As shown in Figure 3, when electrode E2 and E2 ' are heated, promptly by electrical power P _ElE2And P _{ElE2 '}When correspondingly controlling, DOS is in pass-through state work.If the light that transmits in heated waveguide WG1 not arrives middle section, so, as see in the second portion of figure, its symmetric pattern will transmit by waveguide WG1 ', because the refractive index of the refractive index ratio waveguide WG2 ' of WG1 ' is big.If transmission light will continue transmission at the middle section asymmetric mode so in the waveguide WG2 ' of less refractive index is arranged in the waveguide WG2 ' of heating.Refractive index difference between the waveguide WG2/WG2 ' of waveguide WG1/WG1 ' that does not heat and heating is defined as Δ n=0,0025.

As what in the first of Fig. 4, see, if heating electrode E1 and E2 ' promptly use power P _ElE2And P _{ElE2 '}Correspondingly control, DOS so of the present invention is in staggered state work.Identical, above-mentioned refractive index difference are also arranged here.If light transmits in the waveguide WG1 of heating, produce asymmetric mode at middle section so, light will transmit by the waveguide WG2 ' that has than low-refraction of heating.If light transmits in the waveguide WG2 of not heating, produce symmetric pattern at middle section so, light will transmit by waveguide WG1 '.Should be clear and definite, the adiabatic condition of switch not only can keep in the waveguide of input field, but also can keep in the waveguide of output area, if angle θ≤0.1 between two waveguides of input field or output area °, refractive index difference Δ n＞0.0015.

For the DOS of the present invention that demonstrates on the polymeric matrix (schematically describes its structure in Fig. 1 and 2, in Fig. 3 and 4, introduced its function), the light of the laser diode of λ=1.55 μ m is linked to each other with input end 1 or input end 2, and go up measuring light output power Popt at output terminal 1 ' and 2 '.Because definite output power value for TE and TM polarization＜± 0.5dB, so only introduce the result of TM polarization.

When Fig. 5 has shown wavelength X=1.55 μ m as electrical power P _{ElE2 '}The measurement curve of the transport property of function, i.e. heating electrode E2 ' in this case.Here use the firm power P of 65mW _ElE2Control electrode E2 (in illustration, having described control).In order to realize that in the waveguide WG1 of input field S1 and WG2 adiabatic model develops, need such heat control that adds.In this configuration, switch will be in pass-through state work.Connect power P at electricity _{ElE2 '}During 〉=45mW, the measured value of crosstalking＜-25dB.Definite, connect power P _{ElE2 '}This value does not change during＜100mW.

To staggered to state, in Fig. 6, described on polymeric substrates, as electrical power P _{ElE2 '}The transport property of the DOS of the present invention of function.In this case, use the firm power P of 45mW _ElE1Control electrode E1 develops condition with waveguide WG1 and the adiabatic model among the WG2 that satisfies input field S1 once more.If variable, controlled connection performance number P _{ElE2 '}〉=45mW, also can measure so here＜-crossfire value of 25dB.The little deviation of constant power controlling derives from the little deviation of electrode and waveguide in the manufacturing process under these two kinds of on-states.But therefore this do not relate to inventive principle, and each waveguide only can be passed through a kind of definite pattern.

Connect in the configuration switching time＜1ms of the heat on the polymeric substrates-light DOS at these two kinds.

For identical switch, when λ=1.3 μ m, also can produce such transport property, and show similar digital break-make performance (not shown).

Fig. 7 (has described, has had various P in observation _ElE2Value with Fig. 5 the transport property of the DOS on the polymeric substrates of the present invention of identical configuration is arranged) time can be clear that the break-make performance of this DOS can be by regulating to the variable connection power control of the electrode in output area and to the constant basic controlling of input field electrode.Can pick out, " numerical " of this DOS (i.e. the clearly demarcated property of " 0 ", " 1 ") can make to guarantee extraordinary extinction ratio in a very narrow Pel-E2 ' value scope according to regulating with the relation of the constant basic controlling value Pel-E2 of the electrode E2 of input field S1.If this value changes, then the surface is gone out to have the little extinction ratio numeral of fine " robustness " (anti-interference) to connect performance.

Above-mentioned break-make performance solely allows error in process of production, and no longer needs very accurate electric current and Control of Voltage.In addition, for the variation of environment temperature, the break-make performance of the DOS of description is stable.

Claims

1, digital optical switch, it comprises :-input field, wherein have input first waveguide and second waveguide, these two waveguides are approaching mutually gradually, up to its interaction area certain a bit, and connect at this point; And-output area, wherein have the 3rd output waveguide and the 4th output waveguide, from above-mentioned that to overseas certain of interaction area a bit these two output waveguides gradually mutually away from, the waveguide of output area links to each other with the waveguide of input field; And-be used for developing the part that control light spread state influences according to adiabatic model,

It is characterized in that, first input waveguide of input field is with respect to second input waveguide, the 3rd output waveguide of output area is identical mutually on xsect, refractive index with respect to the 4th output waveguide, and they on about the layout of optical propagation direction symmetrically, the adjacent layout with these waveguides of structure electrode with localized variation width, the electrode that is arranged in the input field gets with the electrode design that is arranged in the output area and can be subjected to electric control.

2, according to the digital optical switch of claim 1, it is characterized in that, first input waveguide and second input waveguide with the θ angle (θ＜＜Δ β/γ) approaching mutually on cathetus ground, input field, the 3rd output waveguide and the 4th output waveguide with identical θ angle on cathetus ground, output area mutually away from.

According to the digital optical switch of claim 1, it is characterized in that 3, first input waveguide and second input waveguide curve ground in the input field is approaching mutually; The 3rd output waveguide and the 4th output waveguide in the output area curve ground mutually away from.

According to the digital optical switch of claim 1, it is characterized in that 4, the input waveguide of input field is identical on xsect and refractive index with respect to the output waveguide of output area, and on their layout symmetry.

5, according to the digital optical switch of claim 1, it is characterized in that, first input waveguide and second input waveguide with the θ angle (θ＜＜Δ β/γ) approaching mutually on cathetus ground, input field, the 3rd output waveguide and the 4th output waveguide in the output area curve ground mutually away from.

6, according to the digital optical switch of claim 1, it is characterized in that, first input waveguide and second input waveguide curve ground in the input field is approaching mutually, the 3rd output waveguide and the 4th output waveguide with the θ angle (θ＜＜Δ β/γ) under on cathetus ground, output area mutually away from.

7, according to the digital optical switch of claim 1, it is characterized in that, with the electrode wedge shape ground covering waveguide of the adjacent layout of waveguide.

8, according to the digital optical switch of claim 1, it is characterized in that, with the electrode structure of the adjacent layout of waveguide be wedge shape, and be arranged in the ducting layer.

9, according to the digital optical switch of claim 1, it is characterized in that, electrode adjacent and the electrode design adjacent with output area output waveguide (with input waveguide minute surface symmetry) with the input field input waveguide get can be subjected to automatically controlled.

According to the digital optical switch of claim 1, it is characterized in that 10, electrode adjacent with the input field input waveguide and the electrode design adjacent with output area output waveguide (with the input waveguide point symmetry) get can be automatically controlled.

11, according to the digital optical switch of claim 1, it is characterized in that, select in the material group that waveguide material is enumerated from below: III-V family semiconductor, LiNbO ₃, glass, Si-Ge mixed crystal, SiO ₂And condensate.

12, according to claim 1,2,4, each digital optical switch in 7 and 11, it is characterized in that, in the switch on polymeric matrix, two approaching point-blank waveguide (WG1 in input field (S1) or output area (S2), WG2) or two point-blank away from waveguide (WG1 ', WG2 ') θ angle≤0.1 between °, waveguide (WG1, WG2, WG1 ', WG2 ') Shang Fang electrode (E1, E2, E1 ' and E2 ') across topped these waveguides in a cushion (TB) wedge shape ground, and each electrode among each electrode in input field (S1) (E1 or E2) and output area (S2) (E1 ' or E2 ') all being designed to be can be automatically controlled, makes the refractive index of corresponding waveguide can reach Δ n 〉=0.0015.